A Busy Day For Science @ NASA News – Voyager 1 Flies Out And Star Clusters Zoom In

There are untold numbers of places online that provide all kinds of astronomy news. The CNYO twitter feed is pushing 200 (following, that is. Still working on the follower count) accounts that range from UK Astronomy Clubs (they are exceptionally well organized on the other side of the pond) to equipment vendors to NASA astronauts. The same goes for RSS feeds from astronomy-centric news services, facebook groups, online magazines (or paper magazines with significant online contents), and a multitude of individuals hosting blog sites that report their own observing, study the news for proper amateur digestion, and generally produce really great content.

All that said, there is a lot of the same news online. With a large twitter feed count, you’ll see the same story a half-dozen times within an hour of its official reporting. Imagine following all the major news services to have them all post the same Associated Press tweet over and over and over again. One comes to question the veracity of the news services who happen to post articles hours or days after everyone else.

I subscribed a year ago to the NASA News Release Email List in the hopes of catching all of the major NASA happenings from the original source. The list is free to subscribe to and pumps out about 3000 news releases a year (some days being MUCH busier than others).

One can make their own subscription official by following the text at the footer of all their messages:

This past September 12 was a banner day for NASA News, as NASA made the official announcement of Voyager 1’s departure (sort of) from the Solar System and Hubble scientists reported the largest yet observed cluster of globular clusters (imagine having multiple M13’s in the same low-power field of view!) – featuring a rare image to complement the standard text-only announcements. I’ve included the two releases below (with an extra image showing the position of Voyager 1 – including an actual image of the distant traveler obtained using the Very Long Baseline Array (VLBA) and Green Bank Telescope (GBT).

NASA’s Voyager 1 spacecraft officially is the first human-made object to venture into interstellar space. The 36-year-old probe is about 12 billion miles (19 billion kilometers) from our sun.

New and unexpected data indicate Voyager 1 has been traveling for about one year through plasma, or ionized gas, present in the space between stars. Voyager is in a transitional region immediately outside the solar bubble, where some effects from our sun are still evident. A report on the analysis of this new data, an effort led by Don Gurnett and the plasma wave science team at the University of Iowa, Iowa City, is published in Thursday’s edition of the journal Science.

“Now that we have new, key data, we believe this is mankind’s historic leap into interstellar space,” said Ed Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. “The Voyager team needed time to analyze those observations and make sense of them. But we can now answer the question we’ve all been asking — ‘Are we there yet?’ Yes, we are.”

Voyager 1 first detected the increased pressure of interstellar space on the heliosphere, the bubble of charged particles surrounding the sun that reaches far beyond the outer planets, in 2004. Scientists then ramped up their search for evidence of the spacecraft’s interstellar arrival, knowing the data analysis and interpretation could take months or years.

Voyager 1 does not have a working plasma sensor, so scientists needed a different way to measure the spacecraft’s plasma environment to make a definitive determination of its location. A coronal mass ejection, or a massive burst of solar wind and magnetic fields, that erupted from the sun in March 2012 provided scientists the data they needed. When this unexpected gift from the sun eventually arrived at Voyager 1’s location 13 months later, in April 2013, the plasma around the spacecraft began to vibrate like a violin string. On April 9, Voyager 1’s plasma wave instrument detected the movement. The pitch of the oscillations helped scientists determine the density of the plasma. The particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. Density of this sort is to be expected in interstellar space.

The plasma wave science team reviewed its data and found an earlier, fainter set of oscillations in October and November 2012. Through extrapolation of measured plasma densities from both events, the team determined Voyager 1 first entered interstellar space in August 2012.

“We literally jumped out of our seats when we saw these oscillations in our data — they showed us the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble,” Gurnett said. “Clearly we had passed through the heliopause, which is the long-hypothesized boundary between the solar plasma and the interstellar plasma.”

The new plasma data suggested a timeframe consistent with abrupt, durable changes in the density of energetic particles that were first detected on Aug. 25, 2012. The Voyager team generally accepts this date as the date of interstellar arrival. The charged particle and plasma changes were what would have been expected during a crossing of the heliopause.

“The team’s hard work to build durable spacecraft and carefully manage the Voyager spacecraft’s limited resources paid off in another first for NASA and humanity,” said Suzanne Dodd, Voyager project manager, based at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif. “We expect the fields and particles science instruments on Voyager will continue to send back data through at least 2020. We can’t wait to see what the Voyager instruments show us next about deep space.”

Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft. It is about 9.5 billion miles (15 billion kilometers) away from our sun.

Voyager mission controllers still talk to or receive data from Voyager 1 and Voyager 2 every day, though the emitted signals are currently very dim, at about 23 watts — the power of a refrigerator light bulb. By the time the signals get to Earth, they are a fraction of a billion-billionth of a watt. Data from Voyager 1’s instruments are transmitted to Earth typically at 160 bits per second, and captured by 34- and 70-meter NASA Deep Space Network (DSN) stations. Traveling at the speed of light, a signal from Voyager 1 takes about 17 hours to travel to Earth. After the data are transmitted to JPL and processed by the science teams, Voyager data are made publicly available.

“Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and adding a new chapter in human scientific dreams and endeavors,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “Perhaps some future deep space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their journey.”

Scientists do not know when Voyager 1 will reach the undisturbed part of interstellar space where there is no influence from our sun. They also are not certain when Voyager 2 is expected to cross into interstellar space, but they believe it is not very far behind.

JPL built and operates the twin Voyager spacecraft. The Voyagers Interstellar Mission is a part of NASA’s Heliophysics System Observatory, sponsored by the Heliophysics Division of NASA’s Science Mission Directorate in Washington. NASA’s DSN, managed by JPL, is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions.

The cost of the Voyager 1 and Voyager 2 missions — including launch, mission operations and the spacecraft’s nuclear batteries, which were provided by the Department of Energy — is about $988 million through September.

For a sound file of the oscillations detected by Voyager in interstellar space, animations and other information, visit: www.nasa.gov/voyager

For an image of the radio signal from Voyager 1 on Feb. 21 by the National Radio Astronomy Observatory’s Very Long Baseline Array, which links telescopes from Hawaii to St. Croix, visit: www.nrao.edu (image below – click for a large version).

RELEASE 13-282 – Hubble Uncovers Largest Known Group of Star Clusters, Clues to Dark Matter

Hubble Space Telescope image of largest known population of globular clusters, in Abell 1689 galaxy grouping. Image Credit: NASA/ESA

NASA’s Hubble Space Telescope has uncovered the largest known population of globular star clusters, an estimated 160,000, swarming like bees inside the crowded core of the giant grouping of galaxies known as Abell 1689.

An international team of astronomers used Hubble’s Advanced Camera for Surveys to discover this bounty of stellar fossils and confirm such compact groupings can be used as reliable tracers for dark matter, the invisible gravitational scaffolding on which galaxies are built.

“We show how the relationship between globular clusters and dark matter depends on the distance from the center of the galaxy grouping,” Karla Alamo-Martinez of the Center for Radio Astronomy and Astrophysics of the National Autonomous University of Mexico in Morelia. “In other words, if you know how many globular clusters are within a certain distance, we can give you an estimate of the amount of dark matter.”

Alamo-Martinez is lead author of a paper on the findings published online Sept. 10 and appearing in the Sept. 20 print edition of The Astrophysical Journal, and part of a team led by John Blakeslee of National Research Council Canada’s Herzberg Institute of Astrophysics at the Dominion Radio Astrophysical Observatory in Victoria, British Columbia.

Globular clusters, dense bunches of hundreds of thousands of stars, are the homesteaders of galaxies. They contain some of the oldest surviving stars in the universe. Almost 95 percent of globular cluster formation occurred within the first 1 billion to 2 billion years after our universe was born in the theorized Big Bang 13.8 billion years ago.

Studying globular clusters is critical to understanding the early, intense star-forming events that mark galaxy formation. Understanding dark matter can yield clues on how large structures such as galaxies and galaxy clusters were assembled billions of years ago.

The globular star cluster in Abell 1689 is roughly twice as large as any other population found in previous globular cluster surveys — in comparison, our Milky Way galaxy hosts about 150 — and constitutes the most distant such systems ever studied, at 2.25 billion light-years away. The Hubble study shows most of the globular clusters in Abell 1689 formed near the center of the galaxy grouping, which contains a deep well of dark matter. The farther away from the galaxy core Hubble looked, the fewer globular clusters it detected. This observation corresponded with a comparable drop in the amount of dark matter, based on previous research.

“The globular clusters are fossils of the earliest star formation in Abell 1689, and our work shows they were very efficient in forming in the denser regions of dark matter near the center of the galaxy cluster,” Blakeslee said. “Our findings are consistent with studies of globular clusters in other galaxy clusters, but extend our knowledge to regions of higher dark matter density.”

Peering deep inside the heart of Abell 1689, Hubble detected the visible-light glow of 10,000 globular clusters, some as dim as 29th magnitude, which is 1 one-billionth the faintness of the dimmest star that can be seen with the naked eye. Based on that number, Blakeslee’s team estimated that more than 160,000 globular clusters are huddled within a diameter of 2.4 million light-years.

“Even though we are looking deep into the cluster, we’re only seeing the brightest globular clusters, and only near the center of Abell 1689 where Hubble was pointed,” he said.

The NASA News Release service is a great way to keep track of goings on in the nation’s space program, but goes much farther into all areas of NASA research, including climate research, geology, engineering, and administration. I encourage interested parties to sign up and get at least some of their space science news first-hand – then complain about all the twitter feeds taking so many minutes to report the same.